RE-doped optical fiber lasers are known and have many potentially important uses, e.g., as pump sources for optical fiber amplifiers, or in laser printers. Among the known RE-doped fiber lasers are cladding-pumped fiber lasers (CPFL). See, for instance, U.S. Pat. No. 4,815,079.
Although such cladding-pumped fiber lasers are potentially very useful, we have encountered with at least some such lasers a problem that needs to be overcome before the lasers can be reliably used. Specifically, we have encountered random self-pulsing at the lasing wavelength of Yb-doped CPFLs, and relatively high values of noise in these lasers. FIG. 7 illustrates the problem. It shows the normalized voltage output as a function of time of a photodetector on which the output of an exemplary Yb-doped CPFL is incident.
Such pulsing is detrimental because, for instance, it can give rise to unwanted signal modulation, and may cause damage to the pump laser diodes and/or downstream optical components. In addition, the noise that this pulsing represents makes the laser useless for applications in, for instance, the printer market, where very stable sources are needed. The pulsing is not limited to Yb-doped CPFL but can occur also in other RE-doped optical fiber lasers.
In view of the potential problems that may be caused by self-pulsing and high noise values, it would be highly desirable to have available simple means that can prevent the self-pulsing and high noise in RE-doped optical fiber lasers. This application discloses such means.